1. Field of the Invention
The invention relates to the field of lighting, and in particular, light extraction in illumination systems.
2. Description of the Related Art
A variety of architectural lighting configurations are utilized to provide artificial illumination in a wide variety of indoor and/or outdoor locations. Such illumination systems can include fixed and portable architectural lighting. Various configurations can employ technologies such as incandescent, fluorescent, and/or light emitting diode based light sources.
One type of architectural lighting configuration can be referred to generally as panel lighting. Panel lights may include, for example, fluorescent lighting in a light box behind a plastic lenticular panel. Panel lighting is often configured as planar and square or rectangular and having width and length dimensions significantly greater than a thickness dimension. While the thickness of panel lighting is generally significantly less than corresponding width and length dimensions, it is frequently the case that the thickness of existing panel lighting forces limitations in installation and use. Display front and backlight techniques can be applied to large area (such as 4′×8′) flat panel lighting.
One specific type of panel lighting is flat panel lighting. Flat panel lights are commonly found in flat panel display applications, which include a transparent panel designed to provide illumination from its planar surface. Light is provided into the panel from a light source (e.g., LEDs or a CCFL lamp), which may be positioned along one or more edges of the panel. Light travels throughout the panel, staying within the panel due to total internal reflection at its front planar surface and back planar surface. At some places on the panel, light may be directed out of the panel by a light extraction or turning feature.
Flat light panels can be sized for luminaire or architectural applications. For architectural applications a panel may be about 4′×8′, or made of tiles of smaller dimensions. Some embodiments include two or more flat light panels adjacently disposed. Thus, flat panel lights can be applied to large areas. Flat panel lights can be used as a luminaire or as a partially transparent light panel and screen. For example, a flat panel light may be used as a privacy screen. The panel can be glass, polymer such as acrylic, polyethylene terephthalate, polycarbonate etc. A 4′×8′ panel may require a thickness of about 0.25″ or greater to allow adequate transmission of light along its width, when illuminated from two edges.
In existing panel designs, light extraction features are often grooves or other features cut into the surface of the panel. However, these machined or embossed features are can be inefficient.